Gas turbine engine airfoil

ABSTRACT

An airfoil for a turbine engine includes pressure and suction sides that extend in a radial direction from a 0% span position at an inner flow path location to a 100% span position at an airfoil tip. The airfoil has a relationship between a total chord length and a span position and corresponds to a curve that has an increasing total chord length from the 0% span position to a first peak. The first peak occurs in the range of 45-65% span position, and the curve either remains constant or has a decreasing total chord length from the first peak toward the 100% span position. The total chord length is at the 0% span position in the range of 8.2-10.5 inches (20.8-26.7 cm). The curve is at least a third order polynomial and has an initial positive slope.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/624,240, which was filed on Feb. 17, 2015 and which claims priorityto U.S. Provisional Application No. 61/941,810, which was filed on Feb.19, 2014 and is incorporated herein by reference.

BACKGROUND

This disclosure relates generally to an airfoil for gas turbine engines,and more particularly to a fan or compressor blade and the relationshipbetween the blade's total chord relative to span.

A turbine engine such as a gas turbine engine typically includes a fansection, a compressor section, a combustor section and a turbinesection. Air entering the compressor section is compressed and deliveredinto the combustor section where it is mixed with fuel and ignited togenerate a high-speed exhaust gas flow. The high-speed exhaust gas flowexpands through the turbine section to drive the compressor and the fansection. The compressor section typically includes low and high pressurecompressors, and the turbine section includes low and high pressureturbines.

The propulsive efficiency of a gas turbine engine depends on manydifferent factors, such as the design of the engine and the resultingperformance debits on the fan that propels the engine. As an example,the fan may rotate at a high rate of speed such that air passes over thefan airfoils at transonic or supersonic speeds. The fast-moving aircreates flow discontinuities or shocks that result in irreversiblepropulsive losses. Additionally, physical interaction between the fanand the air causes downstream turbulence and further losses. Althoughsome basic principles behind such losses are understood, identifying andchanging appropriate design factors to reduce such losses for a givenengine architecture has proven to be a complex and elusive task.

SUMMARY

In one exemplary embodiment, an airfoil for a turbine engine includespressure and suction sides that extend in a radial direction from a 0%span position at an inner flow path location to a 100% span position atan airfoil tip. The airfoil has a relationship between a total chordlength and a span position and corresponds to a curve that has anincreasing total chord length from the 0% span position to a first peak.The first peak occurs in the range of 45-65% span position, and thecurve either remains constant or has a decreasing total chord lengthfrom the first peak toward the 100% span position. The total chordlength is at the 0% span position in the range of 8.2-10.5 inches(20.8-26.7 cm). The curve is at least a third order polynomial and hasan initial positive slope.

In a further embodiment of any of the above, the total chord lengthincludes a maximum differential between the maximum and minimum chordlengths along the entire span in the range of 3.0-4.0 inches (7.6-10.2cm).

In a further embodiment of any of the above, the peak is provided by afirst critical point in a range of 60-65% span position.

In a further embodiment of any of the above, a negative slope extendsfrom the critical point to a second critical point in a range of 80-90%span position.

In a further embodiment of any of the above, the second critical pointhas an L/Rd ratio in the range of 0.32 to 0.35.

In a further embodiment of any of the above, a positive slope extendsfrom the second critical point to the 100% span position. The totalchord length is at the 100% span position less than the total chordlength at the peak.

In a further embodiment of any of the above, the peak is provided by acritical point in a range of 50-60% span position.

In a further embodiment of any of the above, a slope from the criticalpoint to an inflection point is substantially zero. The inflection pointis in a range of 70-80% span position.

In a further embodiment of any of the above, a positive slope extendsfrom the inflection point to the 100% span position.

In a further embodiment of any of the above, the 100% span position hasan L/Rd ratio in the range of 0.38 to 0.42.

In a further embodiment of any of the above, the positive slope extendsfrom the inflection point to the 100% span position is constant.

In a further embodiment of any of the above, the peak is provided by acritical point in a range of 40-50% span position.

In a further embodiment of any of the above, a negative slope extendsfrom the critical point to the 100% span position.

In a further embodiment of any of the above, the negative slope isconstant from about a 55% span position to the 100% span position.

In a further embodiment of any of the above, the critical point has anL/Rd ratio in the range of 0.39 to 0.43.

In a further embodiment of any of the above, the airfoil is a fan bladefor a gas turbine engine.

In another exemplary embodiment, a gas turbine engine includes acombustor section that is arranged between a compressor section and aturbine section, a fan section having an array of twenty-six or fewerfan blades and has a low fan pressure ratio of less than 1.55 and ageared architecture coupling the fan section to the turbine section orcompressor section. The fan blades include an airfoil that has pressureand suction sides. The airfoil extends in a radial direction from a 0%span position at an inner flow path location to a 100% span position atan airfoil tip. The airfoil has a relationship between a total chordlength and a span position and corresponds to a curve that has anincreasing total chord length from the 0% span position to a first peak.The first peak occurs in the range of 45-65% span position, and thecurve either remains constant or has a decreasing total chord lengthfrom the first peak toward the 100% span position. The total chordlength is at the 0% span position in the range of 8.2-10.5 inches(20.8-26.7 cm). The curve is at least a third order polynomial and hasan initial positive slope.

In another exemplary embodiment, a gas turbine engine includes acombustor section that is arranged between a compressor section and aturbine section, a fan section has a low fan pressure ratio of less than1.55. The fan blades include an airfoil that has pressure and suctionsides. The airfoil extends in a radial direction from a 0% span positionat an inner flow path location to a 100% span position at an airfoiltip. The airfoil has a relationship between a total chord length and aspan position and corresponds to a curve that has an increasing totalchord length from the 0% span position to a first peak. The first peakoccurs in the range of 45-65% span position, and the curve eitherremains constant or has a decreasing total chord length from the firstpeak toward the 100% span position. The total chord length is at the 0%span position in the range of 8.2-10.5 inches (20.8-26.7 cm). The curveis at least a third order polynomial and has an initial positive slope.

In a further embodiment of any of the above, the low fan pressure ratiois less than about 1.52.

In a further embodiment of any of the above, the low fan pressure ratiois less than about 1.50.

In a further embodiment of any of the above, the low fan pressure ratiois less than about 1.48.

In a further embodiment of any of the above, the low fan pressure ratiois less than about 1.46.

In a further embodiment of any of the above, the low fan pressure ratiois less than about 1.44.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 schematically illustrates a gas turbine engine embodiment.

FIG. 2A is a perspective view of a portion of a fan section.

FIG. 2B is a schematic cross-sectional view of the fan section.

FIG. 2C is a cross-sectional view a fan blade taken along line 2C-2C inFIG. 2B.

FIG. 3A is a schematic view of fan blade span positions.

FIG. 3B is a schematic view of a cross-section of a fan blade section ata particular span position and its chord length.

FIG. 4A illustrates a relationship between total chord and span positionfor a set of first example airfoils.

FIG. 4B illustrates a relationship between total chord and span positionfor a set of second example airfoils.

FIG. 4C illustrates a relationship between total chord and span positionfor a set of third example airfoils.

The embodiments, examples and alternatives of the preceding paragraphs,the claims, or the following description and drawings, including any oftheir various aspects or respective individual features, may be takenindependently or in any combination. Features described in connectionwith one embodiment are applicable to all embodiments, unless suchfeatures are incompatible.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmenter section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flow path B in abypass duct defined within a nacelle 15, while the compressor section 24drives air along a core flow path C for compression and communicationinto the combustor section 26 then expansion through the turbine section28. Although depicted as a two-spool turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with two-spoolturbofans as the teachings may be applied to other types of turbineengines including three-spool architectures. That is, the disclosedairfoils may be used for engine configurations such as, for example,direct fan drives, or two- or three-spool engines with a speed changemechanism coupling the fan with a compressor or a turbine sections.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis X relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a first (or low) pressure compressor 44 and afirst (or low) pressure turbine 46. The inner shaft 40 is connected tothe fan 42 through a speed change mechanism, which in exemplary gasturbine engine 20 is illustrated as a geared architecture 48 to drivethe fan 42 at a lower speed than the low speed spool 30. The high speedspool 32 includes an outer shaft 50 that interconnects a second (orhigh) pressure compressor 52 and a second (or high) pressure turbine 54.A combustor 56 is arranged in exemplary gas turbine 20 between the highpressure compressor 52 and the high pressure turbine 54. A mid-turbineframe 57 of the engine static structure 36 is arranged generally betweenthe high pressure turbine 54 and the low pressure turbine 46. Themid-turbine frame 57 further supports bearing systems 38 in the turbinesection 28. The inner shaft 40 and the outer shaft 50 are concentric androtate via bearing systems 38 about the engine central longitudinal axisX which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path C. The turbines 46, 54 rotationally drivethe respective low speed spool 30 and high speed spool 32 in response tothe expansion. It will be appreciated that each of the positions of thefan section 22, compressor section 24, combustor section 26, turbinesection 28, and fan drive gear system 48 may be varied. For example,gear system 48 may be located aft of combustor section 26 or even aft ofturbine section 28, and fan section 22 may be positioned forward or aftof the location of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five (5:1). Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicyclic geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present invention isapplicable to other gas turbine engines including direct driveturbofans.

The example gas turbine engine includes the fan 42 that comprises in onenon-limiting embodiment less than about twenty-six (26) fan blades. Inanother non-limiting embodiment, the fan section 22 includes less thanabout twenty (20) fan blades. Moreover, in one disclosed embodiment thelow pressure turbine 46 includes no more than about six (6) turbinerotors schematically indicated at 34. In another non-limiting exampleembodiment the low pressure turbine 46 includes about three (3) turbinerotors. A ratio between the number of fan blades 42 and the number oflow pressure turbine rotors is between about 3.3 and about 8.6. Theexample low pressure turbine 46 provides the driving power to rotate thefan section 22 and therefore the relationship between the number ofturbine rotors 34 in the low pressure turbine 46 and the number ofblades 42 in the fan section 22 disclose an example gas turbine engine20 with increased power transfer efficiency.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned divided by lbf of thrust theengine produces at that minimum point. “Low fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.55. Inanother non-limiting embodiment the low fan pressure ratio is less thanabout 1.52. In another non-limiting embodiment the low fan pressureratio is less than about 1.50. In another non-limiting embodiment thelow fan pressure ratio is less than about 1.48. In another non-limitingembodiment the low fan pressure ratio is less than about 1.46. Inanother non-limiting embodiment the low fan pressure ratio is less thanabout 1.44. In another non-limiting embodiment the low fan pressureratio is from 1.1 to 1.45. “Low corrected fan tip speed” is the actualfan tip speed in ft/sec divided by an industry standard temperaturecorrection of [(Tram ° R)/(518.7° R)]^(0.5). The “Low corrected fan tipspeed” as disclosed herein according to one non-limiting embodiment isless than about 1150 ft/second. The “low corrected fan tip speed” asdisclosed herein according to another non-limiting embodiment is lessthan about 1200 ft/second.

Referring to FIG. 2A-2C, the fan blade 42 is supported by a fan hub 60that is rotatable about the axis X. Each fan blade 42 includes anairfoil 64 extending in a radial span direction R from a root 62 to atip 66. A 0% span position corresponds to a section of the airfoil 64 atthe inner flow path (e.g., a platform), and a 100% span positioncorresponds to a section of the airfoil 64 at the tip 66.

The root 62 is received in a correspondingly shaped slot in the fan hub60. The airfoil 64 extends radially outward of the platform, whichprovides the inner flow path. The platform may be integral with the fanblade or separately secured to the fan hub, for example. A spinner 66 issupported relative to the fan hub 60 to provide an aerodynamic innerflow path into the fan section 22.

The airfoil 64 has an exterior surface 76 providing a contour thatextends from a leading edge 68 aftward in a chord-wise direction H to atrailing edge 70, as shown in FIG. 2C. Pressure and suction sides 72, 74join one another at the leading and trailing edges 68, 70 and are spacedapart from one another in an airfoil thickness direction T. An array ofthe fan blades 42 are positioned about the axis X in a circumferentialor tangential direction Y. Any suitable number of fan blades may be usedin a given application.

The exterior surface 76 of the airfoil 64 generates lift based upon itsgeometry and directs flow along the core flow path C. The fan blade 42may be constructed from a composite material, or an aluminum alloy ortitanium alloy, or a combination of one or more of these.Abrasion-resistant coatings or other protective coatings may be appliedto the fan blade 42.

One characteristic of fan blade performance relates to the fan blade'stotal chord relative to a particular span position (R direction).Referring to FIG. 3A, span positions a schematically illustrated from 0%to 100% in 10% increments. Each section at a given span position isprovided by a conical cut that corresponds to the shape of the core flowpath, as shown by the large dashed lines. In the case of a fan bladewith an integral platform, the 0% span position corresponds to theradially innermost location where the airfoil meets the fillet joiningthe airfoil to the platform. In the case of a fan blade without anintegral platform, the 0% span position corresponds to the radiallyinnermost location where the discrete platform meets the exteriorsurface of the airfoil. In addition to varying with span, total chordvaries between a hot, running condition and a cold, static (“on thebench”) condition.

The total chord corresponds to a chord length L extending from theleading edge 68 to the trailing edge 70 at a given span position, asshown in FIG. 3B. The chord length L changes along the span of theairfoil 64 to achieve a desired aerodynamic performance for the fanblade. The total chord may also be expressed as a ratio to the spandistance Rd, where Rd is the radial distance from hub's rotational axisX to the tip of the leading edge 68 and where the ratio is L/Rd. Rd asdisclosed herein according to one non-limiting embodiment is about 35-37inches (0.89-0.94 meters). In another non-limiting embodiment Rd isabout 27-29 inches (0.69-0.74 meters). In another non-limitingembodiment Rd is about 39-41 inches (0.99-1.04 meters). One exampleprior art airfoil has an Rd of about 57-59 inches (1.45-1.50 meters).

In one example prior art airfoil, a peak between positive and negativeslopes is provided in a range of 50% span to 55% span at which point thecurve includes an L/Rd ratio of 0.35-0.36. The total chord L at 0% spanis around 14 inches (35-36 cm).

Example relationships between the total chord length L and the spanposition (PERCENT AVERAGE SPAN), which is the average of the radialposition at the leading and trailing edges 68, 70, are shown in FIGS.4A-4C for several example fan blades, each represented by a curve. Onlyone curve in each graph is discussed for simplicity. Each relationshipstarts with a total chord length at the 0% span position in the range of8.2-10.5 inches (20.8-26.7 cm). The fan blades include a maximumdifferential between the maximum and minimum chord lengths along theentire span in the range of 3.0-4.0 inches (7.6-10.2 cm). The curveshave an increasing total chord length (positive slope from the 0% spanposition to a first peak. The first peak occurs in the range of 45-65%span position, after which the curve either remains generally constant(no slope/no change in total chord length) or has a decreasing totalchord length (negative slope). The example curves are at least a thirdorder polynomial with a generally S-shaped curve having an initialpositive slope. Some notable points are indicated by an “x” on thecurve.

Referring to FIG. 4A, the peak is provided by a critical point in arange of 60-70% span position. The critical point has an L/Rd ratio inthe range of 0.34 to 0.37. A negative slope extends from the criticalpoint to a second critical point in a range of 80-90% span position. Thesecond critical point has an L/Rd ratio in the range of 0.32 to 0.35. Apositive slope extends from the second critical point to the 100% spanposition, and the total chord length at the 100% span position less thanthe total chord length at the peak.

Referring to FIG. 4B, the peak is provided by a critical point in arange of 50-60% span position. A slope from the critical point to aninflection point is substantially zero. The inflection point in a rangeof 70-80% span position. A positive slope extends from the inflectionpoint to the 100% span position. The 100% span position has an L/Rdratio in the range of 0.38 to 0.42. The positive slope extending fromthe inflection point to the 100% span position is generally constant.

Referring to FIG. 4C, the peak is provided by a critical point in arange of 40-50% span position. A negative slope extends from thecritical point to the 100% span position. The negative slope isgenerally constant from about a 55% span position to the 100% spanposition. The critical point has an L/Rd ratio in the range of 0.39 to0.43.

The total chord in a hot, running condition along the span of theairfoils 64 relate to the contour of the airfoil and provide necessaryfan operation in cruise at the lower, preferential speeds enabled by thegeared architecture 48 in order to enhance aerodynamic functionality andthermal efficiency. As used herein, the hot, running condition is thecondition during cruise of the gas turbine engine 20. For example, thetotal chord in the hot, running condition can be determined in a knownmanner using numerical analysis, such as finite element analysis.

It should also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom. Although particular step sequencesare shown, described, and claimed, it should be understood that stepsmay be performed in any order, separated or combined unless otherwiseindicated and will still benefit from the present invention.

Although the different examples have specific components shown in theillustrations, embodiments of this invention are not limited to thoseparticular combinations. It is possible to use some of the components orfeatures from one of the examples in combination with features orcomponents from another one of the examples.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

What is claimed is:
 1. An airfoil for a turbine engine comprising:pressure and suction sides extending in a radial direction from a 0%span position at an inner flow path location to a 100% span position atan airfoil tip, wherein the airfoil has a relationship between a totalchord length and a span position corresponding to a curve having anincreasing total chord length from the 0% span position to a first peak,the first peak occurs in the range of 45-65% span position, the curveeither remains constant or has a decreasing total chord length from thefirst peak toward the 100% span position, wherein the total chord lengthat the 0% span position in the range of 8.2-10.5 inches (20.8-26.7 cm),wherein the curve is at least a third order polynomial having an initialpositive slope.
 2. The airfoil according to claim 1, wherein the totalchord length include a maximum differential between the maximum andminimum chord lengths along the entire span in the range of 3.0-4.0inches (7.6-10.2 cm).
 3. The airfoil according to claim 1, wherein thepeak is provided by a first critical point in a range of 60-65% spanposition.
 4. The airfoil according to claim 3, wherein a negative slopeextends from the critical point to a second critical point in a range of80-90% span position.
 5. The airfoil according to claim 4, wherein thesecond critical point has an L/Rd ratio in the range of 0.32 to 0.35. 6.The airfoil according to claim 4, wherein a positive slope extends fromthe second critical point to the 100% span position, the total chordlength at the 100% span position less than the total chord length at thepeak.
 7. The airfoil according to claim 1, wherein the peak is providedby a critical point in a range of 50-60% span position.
 8. The airfoilaccording to claim 7, wherein a slope from the critical point to aninflection point is substantially zero, the inflection point in a rangeof 70-80% span position.
 9. The airfoil according to claim 8, wherein apositive slope extends from the inflection point to the 100% spanposition.
 10. The airfoil according to claim 9, wherein the 100% spanposition has an L/Rd ratio in the range of 0.38 to 0.42.
 11. The airfoilaccording to claim 9, wherein the positive slope extending from theinflection point to the 100% span position is constant.
 12. The airfoilaccording to claim 1, wherein the peak is provided by a critical pointin a range of 40-50% span position.
 13. The airfoil according to claim12, wherein a negative slope extends from the critical point to the 100%span position.
 14. The airfoil according to claim 13, wherein thenegative slope is constant from about a 55% span position to the 100%span position.
 15. The airfoil according to claim 12, wherein thecritical point has an L/Rd ratio in the range of 0.39 to 0.43.
 16. Theairfoil according to claim 1, wherein the airfoil is a fan blade for agas turbine engine.
 17. A gas turbine engine comprising: a combustorsection arranged between a compressor section and a turbine section; afan section having an array of twenty-six or fewer fan blades, whereinthe fan section has a low fan pressure ratio of less than 1.55; a gearedarchitecture coupling the fan section to the turbine section orcompressor section; and wherein the fan blades include an airfoil havingpressure and suction sides, the airfoil extends in a radial directionfrom a 0% span position at an inner flow path location to a 100% spanposition at an airfoil tip, wherein the airfoil has a relationshipbetween a total chord length and a span position corresponding to acurve having an increasing total chord length from the 0% span positionto a first peak, the first peak occurs in the range of 45-65% spanposition the curve either remains constant or has a decreasing totalchord length from the first peak toward the 100% span position, whereinthe total chord length at the 0% span position in the range of 8.2-10.5inches (20.8-26.7 cm), wherein the curve is at least a third orderpolynomial having an initial positive slope.
 18. A gas turbine enginecomprising: a combustor section arranged between a compressor sectionand a turbine section; a fan section has a low fan pressure ratio ofless than 1.55; and wherein the fan blades include an airfoil havingpressure and suction sides, the airfoil extends in a radial directionfrom a 0% span position at an inner flow path location to a 100% spanposition at an airfoil tip, wherein the airfoil has a relationshipbetween a total chord length and a span position corresponding to acurve having an increasing total chord length from the 0% span positionto a first peak, the first peak occurs in the range of 45-65% spanposition the curve either remains constant or has a decreasing totalchord length from the first peak toward the 100% span position, whereinthe total chord length at the 0% span position in the range of 8.2-10.5inches (20.8-26.7 cm), wherein the curve is at least a third orderpolynomial having an initial positive slope.
 19. The gas turbine engineaccording to claim 18, wherein the low fan pressure ratio is less than1.52.
 20. The gas turbine engine according to claim 19, wherein the lowfan pressure ratio is less than 1.50.
 21. The gas turbine engineaccording to claim 20, wherein the low fan pressure ratio is less than1.48.
 22. The gas turbine engine according to claim 21, wherein the lowfan pressure ratio is less than 1.46.
 23. The gas turbine engineaccording to claim 22, wherein the low fan pressure ratio is less than1.44.